Fluid filled type vibration damping device

ABSTRACT

A vibration damping device including: a rubber elastic body connecting first and second mounting members; a partition member supported on the second mounting member; a pressure-receiving chamber and an equilibrium chamber connected by a first orifice passage; an oscillating plate defining the pressure-receiving chamber; and an electromagnetic actuator for actuating the oscillating plate. The oscillating plate is constituted by a cylinder shaped hole and a piston shaped plate accommodated within the cylinder shaped hole with a gap provided therebetween. An output member of the electromagnetic actuator is linked to the piston shaped plate. A plate spring extending in an axis-perpendicular direction is disposed to an opposite side from the electromagnetic actuator with the piston shaped plate therebetween, with the oscillating plate linked to and supported in an axial direction with respect to the partition member by the plate spring.

INCORPORATED BY REFERENCE

The disclosure of Japanese Patent Application No. 2007-246119 filed onSep. 21, 2007 and No. 2007-337015 filed on Dec. 27, 2007, each includingthe specification, drawings and abstract are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluid filled vibration damping deviceadapted to provide active vibration damping action through control ofpressure fluctuations of a pressure receiving chamber that is filledwith a non-compressible fluid, the control being carried out in a cyclethat corresponds to the frequency of the vibration to be damped.

2. Description of the Related Art

In the field of vibration damping devices such as vibration dampinglinkages or vibration damping supports designed for installation betweencomponents that make up a vibration transmission system, one type ofknown device is a fluid filled type vibration damping device having afirst mounting member and a second mounting member linked by a rubberelastic body; a pressure-receiving chamber whose wall is partiallydefined by the rubber elastic body and an equilibrium chamber whose wallis partially defined by a flexible film, the pressure-receiving chamberand the equilibrium chamber being formed to either side of a partitionmember and filled with a non-compressible fluid; and an orifice passageconnecting the pressure-receiving chamber and the equilibrium chamber.Since this type of fluid filled vibration damping device is able toexhibit vibration damping effect by using flow action, e.g. resonanceaction, of fluid flowing through the orifice passage, application ofsuch devices in automotive engine mounts and the like is a current topicof interest.

Active type fluid filled vibration damping devices are one type of fluidfilled vibration damping device as discussed above. In such an activevibration damping device, typically, another part of the wall of thepressure-receiving chamber will be constituted by an oscillating plate,and an electromagnetic actuator will be disposed to the opposite side ofthe pressure-receiving chamber, with the oscillating plate between them.A coil member making up part of the electromagnetic actuator is fixedlysupported on the second mounting member, and an output member that issubjected to driving force when electrical current is supplied to thecoil member is affixed to the oscillating plate. With this arrangement,oscillation by the oscillating plate is actuated through control ofcurrent to the coil member with reference to the vibration to be damped,in order to control the vibration damping performance through control ofpressure in the pressure-receiving chamber.

The oscillating plate employed in an active vibration damping device ofthis kind will in some instances be formed from a rubber elastic bodyfor example. However, in order to ensure an effective piston surfacearea, it is preferable for the plate to be composed of a rigid member ofmetal, synthetic resin, or the like, as taught in U.S. Pat. No.6,422,546.

However, in the fluid filled vibration damping device disclosed in U.S.Pat. No. 6,422,546, with the aim of providing the oscillating plate withelastically positioned support while ensuring fluid-tightness on thepart of the pressure-receiving chamber, the oscillating plate is linkedto the second mounting member via a supporting rubber elastic body ofannular shape. For this reason, there is a anxiety that, owing topermanent set in fatigue of the supporting rubber elastic body, it willbe difficult to consistently achieve the desired vibration dampingaction. Another problem is that oscillation energy of the oscillatingplate will be consumed through deformation of the supporting rubberelastic body, and thus power consumption will be high.

Accordingly, in Japanese unexamined Patent Publication No.JP-A-2005-291276, the Applicant proposed a fluid filled vibrationdamping device incorporating an oscillating plate of piston design. Inthis fluid filled vibration damping device, a portion of the wall of thepressure-receiving chamber is defined by a cylinder member of hollowround tubular shape, and the output member of the electromagneticactuator is provided at the distal end thereof in the actuationdirection with an oscillating plate of piston shape. A gap is providedbetween the outside peripheral face of the oscillating plate and theinside peripheral face of the cylinder member, while the oscillatingplate is displaceable in the axial direction along the inside peripheralface of the cylinder member. Through appropriate design of the planardimensions and of the gap between the inside peripheral face of thecylinder member and the outside peripheral face of the oscillatingplate, it is possible to control pressure of the pressure-receivingchamber in association with oscillation of the oscillating plate, whileensuring that pressure fluctuations of the pressure-receiving chamberare such that the orifice effect is maintained.

The gap between the inside peripheral face of the cylinder member andthe outside peripheral face of the oscillating plate will besufficiently small so as to inhibit pressure leakage from thepressure-receiving chamber through the gap. Additionally, in order toensure large planar dimensions of the opposed faces of the oscillatingplate and the cylinder member with a view to inhibiting pressure leakagefrom the pressure-receiving chamber, it will be preferable for theinside peripheral section of the cylinder member and of the outsideperipheral section of the oscillating plate to have considerable axiallength.

However, where the gap between the cylinder member and the oscillatingplate is small and their opposed faces extend for considerable length inthe axial direction, there is an anxiety that the oscillating plate willinterfere with the inside peripheral face of the cylinder member.

In particular, owing to factors such as the pressure distribution of thepressure-receiving chamber and twisting displacement of the actuatoroutput shaft, the oscillating plate will tend to interfere with thecylinder inside face through twisting displacement in the axialdirection. When the oscillating plate experiences displacement in theaxial direction while interfering with the cylinder member in this way,not only will the actuation efficiency of the oscillating plate bereduced, but there will also be an anxiety of damage to the opposingfaces of the oscillating plate and/or the cylinder member. Furthermore,if seizing should occur, there is an anxiety that electromagneticactuator may operate improperly of become non-operational, or that noiseand vibration may result.

SUMMARY OF THE INVENTION

It is therefore one object of this invention to provide a fluid filledtype active damping device of novel construction which affords stabledriving displacement of the oscillating plate, and thereby achieveseffective vibration damping action.

The above and/or optional objects of this invention may be attainedaccording to at least one of the following modes of the invention. Thefollowing modes and/or elements employed in each mode of the inventionmay be adopted at any possible optional combinations. It is to beunderstood that the principle of the invention is not limited to thesemodes of the invention and combinations of the technical features, butmay otherwise be recognized based on the teachings of the presentinvention disclosed in the entire specification and drawings or that maybe recognized by those skilled in the art in the light of the presentdisclosure in its entirety.

A principle of the present invention provides a fluid filled typevibration damping device including: a rubber elastic body elasticallyconnecting a first mounting member and a second mounting member, apartition member supported on the second mounting member; apressure-receiving chamber whose wall is partly defined by the rubberelastic body; an equilibrium chamber whose wall is partly defined by aflexible film; the pressure-receiving chamber and the equilibriumchamber being formed to either side of the partition member and filledwith a non-compressible fluid; a first orifice passage connecting thepressure-receiving chamber and the equilibrium chamber; an oscillatingplate defining another part of the wall of the pressure-receivingchamber; and an electromagnetic actuator for actuating oscillation ofthe oscillating plate. The oscillating plate is constituted by includinga cylinder shaped hole having a round tubular inside peripheral faceformed in the partition member, and a piston shaped plate accommodatedwithin the cylinder shaped hole with a gap provided between an outsideperipheral face of the piston shaped plate and the inside peripheralface of the cylinder shaped hole so that the piston shaped plate isaxially displaceable within the cylinder shaped hole, an output memberof the electromagnetic actuator is passed through the flexible film andlinked to the piston shaped plate, and a plate spring extending in anaxis-perpendicular direction is disposed to an opposite side from theelectromagnetic actuator with the piston shaped plate therebetween, withthe oscillating plate being elastically linked to and supported in anaxial direction with respect to the partition member by the platespring.

In the fluid filled vibration damping device constructed according tothe present invention, the oscillating plate at a first side thereof inthe axial direction is positioned and supported in theaxis-perpendicular direction by the output member of the electromagneticactuator; and at the other side thereof in the axial direction ispositioned and supported in the axis-perpendicular direction by theplate spring. By positioning and supporting the oscillating plate in theaxis-perpendicular direction from both sides in the axial direction withrespect to the partition member in this way, it is possible to achieveexcellent suppressant effect against displacement of the oscillatingplate in the axis-perpendicular direction, as well as againstdisplacement in twisting directions.

That is, because the oscillating plate is substantially supported atboth sides of its center axis (both sides in the actuation direction ofthe oscillating plate), the oscillating plate is positioned in proximityto a band of smaller displacement of the medial section rather than atthe location of larger displacement of the free end side during tiltingof the oscillating plate. For this reason, in addition to displacementin the axis-perpendicular direction, twisting deformation of theoscillating plate will be effectively inhibited as well, preventing itfrom interfering with the cylinder shape hole.

Moreover, because the oscillating plate is substantially supported atboth sides of its center axis, problems caused by interference of theoscillating plate with the cylinder shaped hole can be resolved, whilethe gap between the outside peripheral face of the oscillating plate(which is constituted by the piston shaped plate) and the insideperipheral face of the cylinder shaped hole can be made sufficientlysmall, and the opposing sections of the piston shaped plate and thecylinder shaped hole can be given sufficient axial length. The effectiveplanar dimensions of the piston shaped plate may be increased thereby,and pressure leakage from the pressure-receiving chamber through the gapmay be suppressed, thereby affording efficient and stable pressurecontrol of the pressure-receiving chamber.

Moreover, by making possible a smaller gap between the piston shapedplate and the cylinder shaped hole and greater axial length of the gap,the flow resistance of fluid through the gap can be elevated, preventingpressure fluctuations of the pressure-receiving chamber from escapinginto the equilibrium chamber through the gap. This results ineffectively producing passive vibration damping action as well.

Furthermore, owing to the use of the plate spring in the presentinvention, the oscillating plate is allowed to undergo adequatedisplacement in the axial direction, while at the same time beingeffectively positioned in the axis-perpendicular direction. Moreover,since the dimension of the plate spring in the axial direction istypically small, it will be possible to avoid problems in terms ofensuring adequate space or larger size in association with installationof the plate spring in the vibration damping device.

According to one preferred mode of the fluid filled vibration dampingdevice of the present invention, the electromagnetic actuator may employa design whereby the output member is elastically supported with respectto a housing of the electromagnetic actuator by a supporting platespring that extends in the axis-perpendicular direction. With thisarrangement, greater stability of the output member which has beenpositioned in the axis-perpendicular direction by the supporting platespring can be utilized to achieve a higher level of reliability inpositioning of the oscillating plate in the axis-perpendiculardirection.

According to another possible mode of the fluid filled vibration dampingdevice of the present invention, wherein the pressure-receiving chamberis partitioned by a dividing wall member that is disposed in a medialsection of the pressure-receiving chamber in order to form to eitherside of the dividing wall member a first pressure-receiving chamberwhose wall is partly defined by the rubber elastic body and a secondpressure-receiving chamber whose wall is partly defined by theoscillating plate, and a filter orifice is provided for connecting thefirst pressure-receiving chamber and the second pressure-receivingchamber. Specifically, in the first pressure-receiving chamber, pressurefluctuations will be produced directly on the basis of elasticdeformation of the rubber elastic body at times of input of vibration,whereas the second pressure-receiving chamber will be exposed topressure fluctuations of the first pressure-receiving chamber throughthe filter orifice, giving rise to pressure fluctuations in associationwith input of vibration. Here, where the resonance frequency of fluidflowing through the filter orifice is tuned to the frequency range ofproblematical vibration that has been targeted for active vibrationdamping action by the oscillating plate, pressure fluctuations arisingin the second pressure-receiving chamber on the basis of actuatedoscillation of the oscillating plate will be transmitted efficiently tothe first pressure-receiving chamber, utilizing the resonance actionetc. of fluid through the filter orifice. The pressure-receiving chambercomposed of this first pressure-receiving chamber and secondpressure-receiving chamber can thereby be positively and activelycontrolled, and the desired vibration damping action may be attainedwith a higher level of effectiveness.

According to yet another possible mode of the fluid filled vibrationdamping device of the present invention, a second orifice passage isprovided connecting the second pressure-receiving chamber and theequilibrium chamber, with the second orifice passage being tuned to ahigher frequency range than the first orifice passage, the filterorifice is formed in the dividing wall member, and a movable plate isdisplaceably disposed in the filter orifice such that pressure of thefirst pressure-receiving chamber is exerted on a first face of themovable plate while pressure of the second pressure-receiving chamber isexerted on another face of the movable plate. With this arrangement, attimes of input of vibration lying in the tuning frequency range of thefirst orifice passage, the opening of the second oscillating plate onthe pressure-receiving chamber side thereof is covered by the movableplate, thus preventing pressure leakage from the pressure-receivingchamber through the second orifice passage and ensuring a sufficientlevel of fluid flow through the first orifice passage. As a result,vibration damping action based on resonance action of fluid through thefirst orifice passage will be consistently achieved. Also, at times ofinput of vibration lying in the tuning frequency range of the secondorifice passage, even if the first orifice passage (which has been tunedto a lower frequency range than the second orifice passage) becomessubstantially closed off, a sufficient level of fluid flow through thesecond orifice passage will be ensured on the basis of displacement ofthe movable plate due to the relative pressure differential between thefirst pressure-receiving chamber and the second pressure-receivingchamber. Consequently, vibration damping action based on resonanceaction of fluid through the second orifice passage will be effectivelyachieved.

Specifically, according to this mode, vibration damping action againstvibration of multiple frequency ranges will be effectively affordedbased on the flow action, e.g. resonance action, of fluid flowingrespectively through the first orifice passage and the second orificepassage. In particular, since the movable plate is disposed in thefilter orifice, the movable plate and the filter orifice that is tunedto a higher frequency range than the resonance frequency of the secondorifice passage may be realized through a relatively simple structure.Additionally, sufficient space for installing the movable plate will beeffectively ensured thereby achieving both improved vibration dampingperformance and smaller size of the vibration damping device.

The movable plate according to this mode may employ any of a number ofdesigns that regulate pressure fluctuations by inducing displacement ofthe plate based on a relative pressure differential between the firstpressure-receiving chamber and the second pressure-receiving chamber.For example, as taught inter alia in Japanese Unexamined PatentPublication No. JP-A-01-93638, U.S. Pat. No. 7,322,570, or JapaneseUnexamined Patent Publication No. JP-A-2006-97823, the movable plate maybe positioned held in an unattached state within a prescribed holdingarea so as to be finely displaceable in the thickness direction withinthe holding area. Thus, via holes formed in the holding area, pressureof the first pressure-receiving chamber is exerted on one face of themovable plate while pressure of the second pressure-receiving chamber isexerted on the other face of the movable plate, whereby a relativepressure differential between the first pressure-receiving chamber andthe second pressure-receiving chamber will be absorbed on the basis offine displacement of the movable plate within the holding area, andpressure absorption by the movable plate in excess of an allowabledisplacement level will be prevented. Alternatively, it would bepossible to employ a design as taught inter alia in Japanese UnexaminedPatent Publication Nos. JP-A 2000-213586, JP-A-07-71506, orJP-A-11-101294 for example, wherein at least the outside peripheralsection of the movable plate is defined by a partition rubber elasticplate, with the partition rubber elastic plate being attached at itsoutside peripheral edge to the partition member or to the secondmounting member thereby fluid-tightly partitioning the firstpressure-receiving chamber and the second pressure-receiving chamber sothat a relative pressure differential arising between the firstpressure-receiving chamber and the second pressure-receiving chamber andexerted on the respective faces of the partition rubber elastic platewill be absorbed on the basis of elastic displacement and/or elasticdeformation of the partition rubber elastic plate based on this pressuredifferential between the first pressure-receiving chamber and the secondpressure-receiving chamber, while at the same time preventing largepressure absorption through elastic deformation of the partition rubberelastic plate. Alternatively, it would be possible to employ a design astaught in U.S. Pat. No. 7,188,830, whereby a plurality of elasticprojecting portions are disposed on both faces of the movable plate, andthe movable plate is constrained in localized fashion by means of theseelastic projecting portions being held clasped between the walls of theholding area of the movable plate, with the spaces between the walls ofthe holding area and those sections of the movable plate devoid ofelastic projecting portions defining fluid channels that connect thefirst pressure-receiving chamber and the second pressure-receivingchamber with one another.

According to yet another possible mode of the fluid filled vibrationdamping device of the present invention, the cylinder shaped hole isformed in a center section of the partition member so as to extend in adirection of opposition of the pressure-receiving chamber and theequilibrium chamber, with the wall of the equilibrium chamber beingdefined in part by an outside peripheral section of the partition memberabout the cylinder shaped hole, and an outside peripheral face of thepartition member has a tapering contour decreasing in diameter from afirst axial end of a pressure-receiving chamber side thereof towardsanother axial end on an equilibrium chamber side. According to thismode, variable capacity of the flexible film in the equilibrium chamberwill be efficiently ensured, and freedom in design of the flexible filmwill be improved, thereby affording further improvement in tuning of thedesired vibration damping action.

According to yet another possible mode of the fluid filled vibrationdamping device of the present invention, a plurality of plate springsare disposed in a stacked structure by being juxtaposed in a directionof actuation of the oscillating plate. Specifically, while oneconceivable method for increasing the oscillation frequency of theoscillating plate would be to increase the thickness dimension of theplate spring to make it more rigid for example, making the plate springthicker in this way will tend to result in higher stress and significantstrain. In a plate spring, which experiences appreciable metal fatiguedue to repeated elastic deformation experienced during actuation of theoscillating plate, it is important to minimize strain in order to ensureendurance. Accordingly, as taught in this mode, where a stackedstructure composed of a plurality of juxtaposed plate springs isemployed, the plate spring can be made more rigid while at the same timereducing stress transmission and avoiding significant strain. For thisreason, enduring performance of the oscillating plate may be ensured,while further improving the degree of freedom in tuning of theoscillation frequency.

According to still another possible mode of the fluid filled vibrationdamping device of the present invention, a lightening section is formedin each plate spring, and a plurality of plate springs are juxtaposedwith the lightening sections communicating with one another. By sodoing, a zone between the plate springs and the oscillating plate willcommunicate via the lightening sections with a fluid-filled zone whosewall is partly defined by the rubber elastic body. For this reason, thepressure-receiving chamber can be constituted by a zone between theplate springs and the oscillating plate in addition to the fluid-filledzone to the inside of the rubber elastic body, thereby effectivelyensuring adequate capacity of the pressure-receiving chamber. Moreover,when the plate springs induce elastic deformation within thepressure-receiving chamber, the fluid resistance of the plate springswill be lower due to the presence of the lightening sections, therebyreducing energy loss associated with deforming of the plate springs, andhence with actuating oscillation of the oscillating plate. Furthermore,since the spring characteristics of the plate springs can now be tunedthrough appropriate design modification of the shape, size, number etc.of the lightening sections in addition to design modification of theshape, size, etc. of the plate springs, a higher degree of freedom intuning of spring characteristics is afforded thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or other objects, features and advantages of theinvention will become more apparent from the following description of apreferred embodiment with reference to the accompanying drawings inwhich like reference numerals designate like elements and wherein:

FIG. 1 is a vertical cross sectional view of a fluid filled typevibration damping device in the form of an automotive engine mountaccording to one embodiment of the present invention;

FIG. 2 is a top plane view of a partition member of the engine mount ofFIG. 1;

FIG. 3 is a cross sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a top plane view of a partition member body of FIG. 2;

FIG. 5 is a top plane view of an oscillating plate of the engine mountof FIG. 1;

FIG. 6 is a cross sectional view of the oscillating plate taken alongline 6-6 of FIG. 5;

FIG. 7 is a top plane view of a supporting plate spring of the enginemount of FIG. 1;

FIG. 8 is an enlarged cross sectional view taken along line 8-8 of FIG.7;

FIG. 9 is a top plane view of a part of a plate spring of the enginemount of FIG. 1; and

FIG. 10 is an enlarged view in vertical cross section of a part of anengine mount of construction according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is depicted an automotive engine mount10 according to one embodiment of a fluid-filled type vibration dampingdevice of the present invention. This engine mount 10 has a constructionwherein a first mounting member 12 of metal and a second mounting member14 of metal are linked by a main rubber elastic body 16. The firstmounting member 12 is adapted to be mounted onto the vehicle's powerunit (not shown), and the second mounting member 14 is adapted to bemounted onto an automobile body (not shown). The power unit is therebyelastically supported on the vehicle body via the intervening enginemount 10.

Whereas FIG. 1 depicts the engine mount 10 in isolation prior toinstallation in a vehicle, with the engine mount 10 installed in thevehicle, distributed load of the power unit will be input in the mountaxial direction (the vertical direction in FIG. 1), thereby inducingdisplacement of the first mounting member 12 and the second mountingmember 14 in the direction closer together in the mount axial direction,whereupon the main rubber elastic body 16 elastically deforms. In thisinstalled state, principle vibration targeted for damping will be inputapproximately in the mount axial direction. In the descriptionhereinbelow, unless indicated otherwise, vertical direction refers tothe vertical direction in FIG. 1.

More specifically, the first mounting member 12 has an inverted bottomedround tubular shape or round post shape. A screw hole 18 which opensonto the upper end face is provided in the center section of the firstmounting member 12. The first mounting member 12 is attached securely tothe power unit by screw-fastening a member on the power unit side (notshown) to the screw hole 18 using a fastening bolt.

The second mounting member 14 has a large-diameter, generally steppedround tubular shape, with a small-diameter portion 22 extending upwardfrom the inside peripheral edge of a shoulder portion 20 of annularplate shape, and a large-diameter portion 24 extending downward from theoutside peripheral edge of the shoulder portion 20. The axial dimensionof the small-diameter portion 22 is longer than the axial dimension ofthe large-diameter portion 24.

The first mounting member 12 and the second mounting member 14 arepositioned coaxially with one another, with the first mounting member 12positioned facing at a prescribed distance away in the axial directionthe opening at the small-diameter portion 22 end of the second mountingmember 14. The main rubber elastic body 16 is interposed between thefirst mounting member 12 and the second mounting member 14.

The main rubber elastic body 16 is a thick rubber elastic body ofgenerally truncated conical shape. In the center portion of the lowerend of the main rubber elastic body 16, there is formed a large-diameterrecess 26 of inverted conical or semispherical shape opening downward. Asection of the first mounting member 12 extending to its lower end fromits axially medial portion is vulcanization bonded to the upper end ofthe main rubber elastic body 16 so as to be embedded therein, while theinside peripheral face of the small-diameter portion 22 of the secondmounting member 14, at a section thereof extending to its axially medialportion from its upper end section, is juxtaposed against andvulcanization bonded to the outside peripheral face of the lower end ofthe main rubber elastic body 16. The main rubber elastic body 16 isthereby constituted as an integrally vulcanization molded component thatintegrally incorporates the first mounting member 12 and the secondmounting member 14, and one of the openings of the second mountingmember 14 (at top in FIG. 1) is sealed off fluid-tightly by the mainrubber elastic body 16. The inside peripheral face of the small-diameterportion 22 of the second mounting member 14 is sheathed entirely fromits axially medial section to its lower end section by a thin rubberseal layer 28 that is integrally formed with the main rubber elasticbody 16. The rim of the open end of the large-diameter recess 26 in themain rubber elastic body 16 is situated inward in the axis-perpendiculardirection from the inside peripheral face of the rubber seal layer 28,so that an annular step portion 30 of annular shape is formed in theboundary section between the main rubber elastic body 16 and the rubberseal layer 28.

A partition member 32 is attached in the opening section of the secondmounting member 14 on its axial lower side. The partition member 32overall has a generally round block shape, and includes a partitionmember body 34, a first dividing wall plate 36 and a second dividingwall plate 38. In this embodiment, the partition member 32 is made ofmetal material such as aluminum alloy or steel, but it could also bemade from rigid synthetic resin material or the like.

As depicted in FIGS. 2 to 4 as well, an outer flanged portion 40 oflarge-diameter annular shape is integrally formed at the upper edgesection of the partition member body 34. The outside peripheral face ofthe partition member body 34 has a tapered shape gradually decreasing inoutside diameter dimension from top to bottom.

A circular center hole 42 is formed extending in the axial directionthrough the center section of the partition member body 34 so as topenetrate the upper and lower end faces of the partition member body 34.A step portion 44 of annular shape is formed in the peripheral wall ofthe center hole 42 in its generally axial center section, with thediameter dimension of the center hole 42 in its upper section to oneside of the step portion 44 being larger compared to the diameterdimension in its lower section. A cylinder shaped hole 46 according tothis embodiment is defined by this lower section of the center hole 42.An inner flanged portion 48 is integrally formed at the lower openingsection of the cylinder shaped hole 46. A plural number of screw holes50 are disposed prescribed distances apart in the circumferentialdirection, in the step portion 44 and around the upper rim of the centerhole 42. The diametrically medial section or outer peripheral section ofthe outer flanged portion 40 is perforated in the thickness direction(the vertical in FIG. 1) by a connecting window 52. As will be apparentfrom the above description, the cylinder shaped hole 46 is formed so asto extend in the axial direction through the center section of thepartition member 32 (the partition member body 34), and the outerperipheral section of the partition member 32 around the cylinder shapedhole 46 is defined by a tapered shape of decreasing diameter from afirst axial end (at top in FIG. 1) to the other.

A block shaped portion 54 is disposed projecting diametrically outwardfrom a single location along the circumference of the peripheral wallsection of the partition member body 34, and a connecting passage 56extends in tunnel form through the block shaped portion 54. Theconnecting passage 56 extends continuously with unchanging oblong crosssection in the diametrical direction through the partition member body34, with a first end (face) thereof opening onto the peripheral wallface of the center hole 42 of the partition member body 34 at a locationabove the step portion 44, and with the other end (face) opening ontothe diametrically outward end face of the block shaped portion 54.

The first dividing wall plate 36 has a shallow, generally circularsaucer shape whose base portion is penetrated by through-holes 58composed of a plurality of small holes; and a rimming portion 60 ofannular shape is integrally formed at its upper lip. The rimming portion60 extends parallel to the base portion of the first dividing wall plate36, at a location above the base portion. The outside diameter dimensionof the base portion of the first dividing wall plate 36 is large incomparison with the diameter dimension of the large-diameter section atthe upper side of the center hole 42 of the partition member body 34,and insertion holes 64 are formed penetrating the outside peripheralsection of the base portion at locations corresponding to the screwholes 50 of the partition member body 34.

Meanwhile, the second dividing wall plate 38 has a shallow, generallybottomed cylindrical shape, with a large-diameter outer flanged portion66 formed at the lip of the opening. In other words, the second dividingwall plate 38 has the form of a thin circular disk shape with a circularrecess formed in its center section. The outside diameter dimension ofthe outer flanged portion 66 is approximately identical to the outsidediameter dimension of the outer flanged portion 40 of the partitionmember body 34, and is larger in comparison with the outside diameterdimension of the rimming portion 60 of the first dividing wall plate 36.The outside diameter dimension of the peripheral wall of the seconddividing wall plate 38 is slightly smaller than the diameter dimensionof the large-diameter section at the upper side of the center hole 42 ofthe partition member body 34. Furthermore, the axial length of theperipheral wall of the second dividing wall plate 38 is smaller incomparison with the axial length of the large-diameter section.Through-holes 68 composed of a plurality of small holes are formedpenetrating the base portion of the second dividing wall plate 38.Additionally, insertion holes 70 are formed penetrating thediametrically medial section or inside peripheral section of the outerflanged portion 66, at locations corresponding to the screw holes 50 ofthe partition member body 34 and to the insertion holes 64 of the firstdividing wall plate 36.

The peripheral wall of the second dividing wall plate 38 is slipped intothe upper opening section of the center hole 42 of the partition memberbody 34, and the outer flanged portion 66 of the second dividing wallplate 38 is juxtaposed against the outer flanged portion 40 of thepartition member body 34. Furthermore, the outside peripheral section ofthe base of the first dividing wall plate 36 is juxtaposed against thediametrical inside peripheral section or medial section of the outerflanged portion 66 of the second dividing wall plate 38, while the screwholes 50 of the partition member body 34, the insertion holes 70 of thesecond dividing wall plate 38, and the insertion holes 64 of the firstdividing wall plate 36 are aligned overlapping one another in the axialdirection. Fastening bolts are then passed through the insertion holes64, 70 in the first and second dividing wall plates 36, 38, and fastenedby screwing into screw holes 50 of the partition member body 34. Thepartition member 32 constituted thereby has a form in which the upperopening of the center hole 42 of the partition member body 34 has beencovered by the first and second dividing wall plates 36, 38. The baseportion of the second dividing wall plate 38 and the step portion 44 ofthe center hole 42 in the partition member body 34 are now positioned inopposition a prescribed distance apart in the axial direction.

The rimming portion 60 of the first dividing wall plate 36 and the outerflanged portion 66 of the second dividing wall plate 38 are positionedin opposition a prescribed distance apart in the axial direction, withthe lower end face of the rimming portion 60, the outside peripheralface of the peripheral wall of the first dividing wall plate 36, and theupper end face of the outer flanged portion 66 cooperating to define aperipheral groove 62 having a cross section that opens with slotcontours diametrically outward in the outside peripheral section of thepartition member 32, and extends continuously all the way around itscircumference.

Furthermore, by covering the opening section of the second dividing wallplate 38 with the base portion of the first dividing wall plate 36, acircular zone 72 that extends with generally unchanging circular crosssection in the axial direction is formed between the center of the baseportion of the first dividing wall plate 36 and the center portion ofthe second dividing wall plate 38.

The partition member 32 of the above design is inserted in the axialdirection into the second mounting member 14 from its bottom opening,and the rimming portion 60 of the first dividing wall plate 36 isjuxtaposed against the annular step portion 30 of the main rubberelastic body 16, while the outside peripheral section of the outerflanged portion 66 of the second dividing wall plate 38 is juxtaposedagainst the shoulder portion 20 via the intervening rubber seal layer 28of the second mounting member 14. With this arrangement, the insertedend of the partition member 32 in the axial direction is regulated withrespect to the second mounting member 14.

A diaphragm 74 (the flexible film) is disposed below the partitionmember 32. The diaphragm 74 is formed from a thin circular rubber filmhaving ample slack. A fastener fitting 76 is vulcanization bonded to theoutside peripheral edge of the diaphragm 74. The fastener fitting 76 hasa design with an inner flanged portion that projects diametricallyinward integrally disposed at the lower end section of a large-diameterring. The diaphragm 74 is vulcanization bonded at its outside peripheraledge to the inside peripheral edge of the fastener fitting 76, while athin seal rubber layer 78 that is integrally formed with the diaphragm74 is vulcanization bonded over generally the entire inside peripheralface of the fastener fitting 76.

The fastener fitting 76 is, slipped inside the second mounting member 14in the axial direction from the opening on its lower side (thelarge-diameter portion 24 side), and the upper edge of the fastenerfitting 76 is then juxtaposed in the axial direction against the insideperipheral section of the shoulder portion 20 of the second mountingmember 14 via the intervening seal rubber layer 78, while the insideperipheral edge on the lower side of the fastener fitting 76 isjuxtaposed in the axial direction against the outside peripheral sectionof the outer flanged portion 40 of the partition member body 34 via theintervening seal rubber layer 78.

Further, a bracket member 80 of round tubular shape is fastened fittingexternally about the second mounting member 14. This bracket member 80is utilized to fasten the partition member 32 and the diaphragm 74 tothe second mounting member 14. Specifically, the bracket member 80includes a middle tube fitting 82 having a thick-walled generally roundtubular shape and end plate fittings 84 a, 84 b of annular plate shapethat are juxtaposed against the axial ends of the middle tube fitting82. The fittings 82, 84 a, 84 b are mated in the axial direction andfastened together with bolts. With the shoulder portion 20 of the secondmounting member 14 and the fastener fitting 76 of the diaphragm 74inserted axially between the upper end plate fitting 84 a and the middletube fitting 82, the bracket member 80 is fastened to the secondmounting member 14 by bolting together the end plate fitting 84 a andthe middle tube fitting 82. In association with bolting together the endplate fitting 84 a and the middle tube fitting 82, the shoulder portion20 of the second mounting member 14 and the fastener fitting 76 ispositioned clamped in the axial direction, with the rimming portion 60of the first dividing wall plate 36 and the annular step portion 30 ofthe main rubber elastic body 16, the outside peripheral section of theouter flanged portion 66 of the second dividing wall plate 38 and thediametrically inside peripheral section or medial section of theshoulder portion 20 of the second mounting member 14, and the upper endsection of the fastener fitting 76 and the outside peripheral section ofthe shoulder portion 20 respectively juxtaposed fluid-tightly via theintervening rubber seal layers 28, 78 etc. By so doing, throughfastening of the bracket member 80 to the second mounting member 14 thepartition member 32 and the diaphragm 74 is fixedly attached to thesecond mounting member 14, while the lower opening of the secondmounting member 14 is blocked off fluid-tightly by the partition member32 and the diaphragm 74. By then fastening the bracket member 80 to acomponent on the vehicle body side (not shown), the second mountingmember 14 is fixedly mounted onto the vehicle body.

By thusly attaching the partition member 32 and the diaphragm 74 to theintegrally vulcanization molded component of the main rubber elasticbody 16 incorporating the first and second mounting members 12, 14, apressure-receiving chamber 86 whose wall is partly defined by the mainrubber elastic body 16 and which gives rise to pressure fluctuations attimes of vibration input is defined to a first axial side of thepartition member 32 (at top in FIG. 1), within the area of thelarge-diameter recess 26 of the main rubber elastic body 16 that hasbeen blocked off by the partition member 32. To the other axial side ofthe partition member 32 (at bottom in FIG. 1) there will be formed anequilibrium chamber 88 whose wall is partly defined by the diaphragm 74and which readily allows change in volume. The pressure-receivingchamber 86 and the equilibrium chamber 88 are filled with anon-compressible fluid. Water, an alkylene glycol, a polyalkyleneglycol, silicone oil, or the like may be employed as the sealednon-compressible fluid, but with a view to effectively achievingvibration damping action based on flow action, e.g. resonance action, ofthe fluid, it is especially preferable to use a low-viscosity fluid of0.1 Pa·s or lower. Sealing of the non-compressible fluid within thepressure-receiving chamber 86 and the equilibrium chamber 88 may beaccomplished advantageously, for example, by attaching the partitionmember 32 and the diaphragm 74 to the main rubber elastic body 16incorporating the first and second mounting members 12, 14 while thesecomponents are submerged in the non-compressible fluid. From the abovediscussion it is appreciated that the wall of the equilibrium chamber 88is partly defined by the tapered outside peripheral section of thepartition member 32 (the partition member body 34) around the cylindershaped hole 46.

In association with the partition member 32 being attached to the secondmounting member 14, the open section of the peripheral groove 62 of thepartition member 32 is juxtaposed fluid-tightly against the insideperipheral face of the second mounting member 14 via the interveningrubber seal layer 28 that sheathes the second mounting member 14, sothat the peripheral groove 62 is closed off fluid-tightly. The insideperipheral face of the second mounting member 14 and the walls of theperipheral groove 62 are thereby cooperate to define a first orificepassage 90 that extends for a prescribed length in the circumferentialdirection through the outside peripheral section of the partition member32. A first end of this first orifice passage 90 connects to thepressure-receiving chamber 86 via a connecting window (not shown) thatpenetrates the peripheral wall of the first dividing wall plate 36,while the other end of the first orifice passage 90 connects to theequilibrium chamber 88 through a connecting window penetrating thesecond dividing wall plate 38 and the connecting window 52 of thepartition member body 34, which windows have been aligned with oneanother in axial direction. The pressure-receiving chamber 86 and theequilibrium chamber 88 thereby communicate with each other through thefirst orifice passage 90, allowing fluid flow between the two chambers86, 88 through the first orifice passage 90.

An oscillating plate 92 composed of a piston shaped plate is disposed inthe cylinder shaped hole 46 of the partition member 32. As depicted inFIGS. 5 and 6, the oscillating plate 92 has a thin, generally circulardisk shape, and is made of rigid synthetic resin material, metal, or thelike. A boss shaped projection 94 having a small-diameter cylindricalshape projects upward from the center section of the oscillating plate92, and the borehole of the boss shaped projection 94 opens onto thelower end face of the oscillating plate 92 so that an insertion hole 96is formed on the center axis of the oscillating plate 92. Additionally,a rim shaped projection 98 of generally round cylindrical shape isformed on the outside peripheral edge of the oscillating plate 92,projecting downward in the axial direction.

The oscillating plate 92 and the cylinder shaped hole 46 are arrangedcoaxially, with the rim shaped projection 98 of the oscillating plate 92positioned along the peripheral wall of the cylinder shaped hole 46 ofthe partition member 32. The oscillating plate 92 is positioned inopposition to and a prescribed distance away in the axial direction fromthe base portion of the second dividing wall plate 38 which covers theupper opening of the center hole 42 of the partition member body 34.Here, small gap 100 is formed about the entire perimeter between theperipheral wall of the cylinder shaped hole 46 and the outsideperipheral section of the oscillating plate 92 having the rim shapedprojection 98, and due to the presence of this gap 100, an appropriatelevel of axial displacement of the oscillating plate 92 is allowed.While no particular limitation is imposed as to whether fluid flow etc.can arise through this gap 100, in this embodiment, the gap 100 is smallenough that substantially no fluid flow etc. will take place through it.As a result, the lower opening of the center hole 42 of the partitionmember body 34 will be substantially blocked off by the oscillatingplate 92.

The zone between the second dividing wall plate 38 and the oscillatingplate 92 in the partition member 32 intercommunicates with thepressure-receiving chamber 86 through the through-holes 58, 68 thatpenetrate the first and second dividing wall plates 36, 38 and throughthe circular zone 72 between the first dividing wall plate 36 and thesecond dividing wall plate 38, and this zone is filled with the samenon-compressible fluid as the pressure-receiving chamber 86.Specifically, through the through-holes 58, 68 and the circular zone 72the zone between the oscillating plate 92 and the second dividing wallplate 38 is subject to pressure fluctuations arising in thepressure-receiving chamber 86, and thus the zone functions as part ofthe pressure-receiving chamber 86. As will be appreciated from thedescription above, in the pressure-receiving chamber 86, the oscillatingplate 92 defines another part of the wall different from that defined bythe main rubber elastic body 16.

In other words, to a first side of the first and second dividing wallplates 36, 38 (at top in FIG. 1) of the partition member 32, there isformed a first pressure-receiving chamber 102 whose wall is partlydefined by the main rubber elastic body 16, while to the other side ofthe first and second dividing wall plates 36, 38 (at bottom in FIG. 1)of the partition member 32, there is formed a second pressure-receivingchamber 104 whose wall is partly defined by the oscillating plate 92.The pressure-receiving chamber 86 incorporates this firstpressure-receiving chamber 102 and second pressure-receiving chamber 104in its design. It will be appreciated from the above description thatthe dividing wall member dividing the pressure-receiving chamber 86incorporates the first dividing wall plate 36 and the second dividingwall plate 38 in its design. Additionally, the filter orifice throughwhich the first pressure-receiving chamber 102 and the secondpressure-receiving chamber 104 intercommunicate incorporates thethrough-holes 58, 68 that have been formed in the first and seconddividing wall plates 36, 38 and the circular zone 72 in its design.

In this embodiment in particular, the resonance frequency of fluidflowing through the filter orifice that incorporates the aforementionedthrough-holes 58, 68 and the circular zone 72 has been tuned to a highfrequency range on the order of 80 to 100 Hz corresponding to medium- orhigh-speed rumble which has been targeted for active vibration dampingby the oscillating plate 92.

The connecting passage 56 that has been formed in the partition memberbody 34 connects at a first end thereof to the second pressure-receivingchamber 104, while the other end of the connecting passage 56 connectsto the equilibrium chamber 88. That is, the connecting passage 56constitutes a second orifice passage 106 connecting the secondpressure-receiving chamber 104 and the equilibrium chamber 88 to oneanother and allowing flow of fluid between the two chambers 88, 104through the second orifice passage 106.

In this embodiment in particular, the resonance frequency of fluidflowing through the first orifice passage 90 is tuned, for example, soas to produce effective vibration damping action (high attenuatingaction) against vibration in a low-frequency range of about 10 Hzcorresponding to engine shake, on the basis of resonance action of thefluid. Meanwhile, the resonance frequency of fluid flowing through thesecond orifice passage 106 is tuned, for example, so as to produceeffective vibration damping action against vibration in amedium-frequency range of about 20 to 40 Hz corresponding to idlingvibration or low speed rumble, on the basis of resonance action of thefluid. That is, the tuning frequency of the second orifice passage 106is set to a higher frequency range than the tuning frequency of thefirst orifice passage 90, and the tuning frequency of the filter orificedefined by the aforementioned through-holes 58, 68 and the circular zone72 is set to a higher frequency range than the first and second orificepassages 90, 106. Tuning of the first orifice passage 90, the secondorifice passage 106, and the filter orifice may be accomplished, forexample, through adjustment of the passage length and passage crosssectional area of the orifice passages while giving consideration tocharacteristic values based on the rigidity of the walls of thepressure-receiving chamber 86 and the equilibrium chamber 88, i.e. onthe levels of elastic deformation by the main rubber elastic body 16 andby the diaphragm 74 corresponding to pressure change levels necessary toproduce a certain change in unit volume of the chambers 86, 88.Typically, the frequency at which the phase of pressure fluctuationstransmitted through the orifice passage changes and assumes theresonance state can be understood as the tuning frequency of the orificepassage.

A movable plate 108 is positioned housed within the circular zone 72 ofthe partition member 32. This movable plate 108 has a generally circulardisk shape that is slightly smaller than the circular zone 72, and ismade of a rubber elastic body. A gap is formed all the way around thecircumference between the peripheral wall of the circular zone 72 (i.e.the peripheral wall second dividing wall plate 38) and the outsideperipheral edge of the movable plate 108. The thickness dimension of themovable plate 108 is smaller in comparison with the axial dimension ofthe circular zone 72. The pressure of the first pressure-receivingchamber 102 is exerted on a first face of the movable plate 108 (at topin FIG. 1) via the through-holes 58 in the first dividing wall plate 36,while the pressure of the second pressure-receiving chamber 104 isexerted on the other face of the movable plate 108 (at bottom in FIG. 1)via the through-holes 68 in the second dividing wall plate 38. Themovable plate 108 is thereby constituted so as to be displaceable in theaxial direction within the circular zone 72 on the basis of a relativepressure differential between the first pressure-receiving chamber 102and the second pressure-receiving chamber 104.

Guide shaft portions 110, 110 are disposed in the center section of themovable plate 108 so as to project outward to either side in the axialdirection. With the movable plate 108 positioned housed within thecircular zone 72, each guide shaft portion 110 is displaceably insertedinto an insertion hole provided in the center section of the firstdividing wall plate 36 which defines the upper wall of the circular zone72 and of the second dividing wall plate 38 which defines its lowerwall, thereby positioning the movable plate 108 in theaxis-perpendicular direction with respect to the circular zone 72, andapproximately aligning the center axis of the movable plate 108 with thecenter axis of the engine mount 10 (the mount axis). Since the movableplate 108 has a corrugated shape on either face, due to the smallerstriking area of the movable plate 108 against the first dividing wallplate 36 and the second dividing wall plate 38, noise is reduced, whileat the same time ensuring large effective surface area of the movableplate 108 so that pressure of the first and second pressure-receivingchambers 102, 104 is efficiently exerted on the movable plate 108.

In this embodiment in particular, the resonance frequency of the movableplate 108 is tuned to a medium frequency range, such as idling vibrationor medium speed rumble, that lies within the same range as the tuningfrequency range of the second orifice passage 106, and is set to a lowerfrequency range compared to the high range of oscillation frequency ofthe oscillating plate 92 and the resonance frequency of the filterorifice.

A connector rod 112 is vulcanization bonded to the center section of thediaphragm 74. The connector rod 112 is a rigid rod shaped member thatextends in the axial direction, and is provided at a first axial end (attop in FIG. 1) with a screw hole 114 that opens onto the first end face;its other side in the axial direction is elongated in the axialdirection and is provided at its distal end section with a male threadportion 116. A rimming portion 118 which flares diametrically outward isintegrally formed in the axially medial section of the connector rod112, and the center section of the diaphragm 74 is vulcanization bondedonto substantially the entire surface of the rimming portion 118. Theconnector rod 112 body is thereby vulcanization bonded to the diaphragm74 so as to penetrate through the center section of the diaphragm 74.

An electromagnetic actuator 120 that actuates oscillation of theoscillating plate 92 is positioned below the second mounting member 14.The electromagnetic actuator 120 in this embodiment employs a knowndesign, and since it would be possible to employ a design like thatdisclosed for example in Japanese Unexamined Patent Publication No.JP-A-2003-339145, the actuator need not be discussed in detail hereinexcept to note that a yoke member 124 which constitutes the stator ispositioned spaced apart to the outside peripheral side of a movablemember 122 which constitutes the slider. Coils 126, 127 and permanentmagnets 128 are attached to the yoke member 124, and through the actionof electromagnetic force generated between the movable member 122 andthe yoke member 124 when electrical current flows to the coils 126, 127,the movable member 122 is actuated in the axial direction relative tothe stator (the yoke member 124).

Specifically, the yoke member 124 is formed of a laminated steel sheetmade of ferromagnetic material, and while not depicted explicitly in thedrawings, has a design in which a pair of magnetic pole portions 130,130 project in opposition along an axis-perpendicular direction on theinside peripheral face from a ring shaped outer peripheral magneticpath. The coils 126, 127 are installed on the pair of magnetic poleportions 130, 130 by being wound about the perimeter at their respectiveprojecting distal end sections. Each of the coils 126, 127 is sheathedby an electrical insulating layer 132. Further, four permanent magnets128 that are superposed along the lamination direction of the laminatedsteel sheet are affixed to the inside peripheral face of the pair ofmagnetic pole portions 130, 130. The inside peripheral face of each ofthe permanent magnets 128 is magnetized to one of S and N polarity,while the outside peripheral face of each of the permanent magnets 128is magnetized to the other of S and N polarity. The four permanentmagnets 128 are arranged with their magnetic poles differing from oneanother in the superposition direction. In this embodiment, fourpermanent magnets 128 are disposed in each coil 126, 127, accommodatedwithin the approximate center in the axial direction.

The housing 136 of the electromagnetic actuator 120 is positioned to theoutside peripheral side of the yoke member 124. The design of thehousing 136 incorporates a large-diameter tubular portion 138 thatextends in the axial direction, and an annular plate portion 140 ofgenerally annular plate shape that is fastened to the upper end sectionof the tubular portion 138 and spreads out in the circumferentialdirection. The yoke member 124, which is housed within the tubularportion 138 while sandwiched in the axial direction by a pair of outertubular washers (spacers) 141, 141, is fixedly supported suspended fromthe annular plate portion 140 by passing elongated fastening bolts 139through it in the axial direction and then securing nuts 135 onto thedistal ends thereof.

The housing 136 is also provided with a lead wire 142. A first end ofthe lead wire 142 connects to the coils 126, 127 inside the housing 136,while the other end of the lead wire 142 extends out from the outsideperipheral face of the housing 136 and hooks up to a power supply 144.This enables the coils 126, 127 to be supplied with electrical currentfrom the power supply 144 through the lead wire 142. As the power supply144, it would be possible to employ the installed power supply for thecar's electrical system, for example.

Meanwhile, the movable member 122 is disposed to the inside of the yokemember 124. The design of the movable member 122 incorporates anactuating rod 154 of elongated tube shape, a plurality of magneticplates 155, and a plurality of inner tubular washers (spacers) 156 ofround tubular shape larger in diameter than the actuating rod 154. Acollar 158 that flares diametrically outward is integrally formed in theupper part of the actuating rod 154.

The magnetic plates 155 are composed of ferromagnetic material havingplate shape, with an insertion hole formed in the center. The insidediameter dimension of this insertion hole is slightly larger than theactuating rod 154. The length of magnetic plates 155 at their two endedges (length in the left-right direction in FIG. 1) is shorter by aprescribed amount than the distance between the opposing faces of thepair of permanent magnets 128, 128 that have been positioned inopposition in the axis-perpendicular direction. The outside diameterdimension of the inner tubular washers (spacers) 156 is smaller than thedistance between the opposing faces of the coils 126, 127 in theaxis-perpendicular direction.

With a pair of assemblies, each composed of three magnetic plates 155stacked in the axial direction, positioned in opposition in the axialdirection to either side of the center inner tubular washer 156 b, andwith inner tubular washers 156 a, 156 c juxtaposed from outside in theaxial direction against the respective stacked magnetic plate 155assemblies, the magnetic plates 155 and the inner tubular washers 156 a,b, c are slipped about the outside of the actuating rod 154. Themagnetic plates 155 are arranged thereby so as to project outward in theaxis-perpendicular direction from the actuating rod 154, with theaxis-perpendicular projecting distal ends (outside peripheral end edges)of the magnetic plates 155 positioned in the axially medial section ofthe respective coils 126, 127, and positioned in opposition to thepermanent magnets 128 in the axis-perpendicular direction. The axialdistance separating the pair of assemblies of three magnetic plates 155is smaller than the inside diameter dimension of the coils 126, 127.

The end of the connector rod 112 on the opposite side of the rimmingportion 118 from the screw hole 114 is slipped into the actuating rod154, and a ring shaped spacer 159 is installed fitting about the outsideof the male thread portion 116 located at the distal end section of theconnector rod 112 which is positioned projecting axially outward fromthe actuating rod 154, and a fastening nut 160 is then threaded andfastened thereon. Due to the fastening force of the fastening nut 160that has been threaded onto the connector rod 112, the magnetic plates155 and the inner tubular washers 156 is clamped in the axial directionbetween the fastening nut 160 and the collar 158 of the actuating rod154, and fastened to the actuating rod 154.

Furthermore, a plurality of supporting plate springs 146 are disposedbetween the movable member 122 and the yoke member 124. As depicted inFIGS. 7 and 8, the supporting plate springs 146 have thin annular diskshape made of spring steel or the like, with a center hole 147 ofcircular shape formed in the center section. As lightening sections, aplurality of slits 148 are formed in the diametrically medial section ofthe supporting plate spring 146, and it will be possible to adjust thesubstantial effective spring length of the supporting plate spring 146and to tune its spring characteristics through appropriate designmodification of the shape, size, number and/or locations of these slits148. The outside peripheral section of the supporting plate spring 146is perforated by a plurality of bolt insertion holes 150. In thisembodiment in particular, the plurality of slits 148 and the pluralityof bolt insertion holes 150 are respectively given identical form andare respectively formed at equidistant intervals in the circumferentialdirection, thereby eliminating the need to align the supporting platesprings 146 in the circumferential direction.

At least one of these supporting plate springs 146 is positioned to oneaxial side (at top in FIG. 1) of the coil 126, 127. With the actuatingrod 154 passed through the center hole 147 of the supporting platespring 146 and with the inside peripheral section of the supportingplate spring 146 secured clamped between the collar 158 of the actuatingrod 154 and the inner tubular washer 156, is supported thereby on themovable member 122. Additionally, at least one more of the supportingplate springs 146 is positioned to the other axial side (at bottom inFIG. 1) of the coil 126, 127. With the actuating rod 154 passed throughthe center hole 147 of the supporting plate spring 146 and with theinside peripheral section of the supporting plate spring 146 securedclamped between the inner tubular washer 156 and the spacer 159, issupported thereby on the movable member 122.

Fastening bolts 139 for securing the yoke member 124 to the housing 136are passed through each of the bolt insertion holes 150 that have beenformed in the outside peripheral section of each of the supporting platesprings 146. The outside peripheral section of the supporting platesprings 146 are clasped, via a ring shaped washer 161, between one ofthe outer tubular washers 141 and the annular plate portion 140, and viaanother ring shaped washer 161, between the other outer tubular washer141 and the nuts 135. The outside peripheral sections of the supportingplate springs 146 are secured clamped in the axial direction, andsupported on the yoke member 124 through screw fastening of thefastening bolts 139 and the nuts 135.

With this arrangement, the movable member 122 is elastically supportedat both axial sides by the supporting plate springs 146 which extend inthe axis-perpendicular direction, and the movable member 122 ispositioned concentrically with the housing 136 incorporating the yokemember 124, and is supported displaceably in the axial direction to theinside of the yoke member 124. Additionally, the pair of assembliescomposed of three magnetic plates 155 stacked adjacently in the axialdirection is positioned in opposition to the permanent magnets 128 ofthe yoke member 124 across a small gap in the axis-perpendiculardirection.

In this embodiment in particular, the supporting plate springs 146 whichsupport the movable member 122 at both of its axial sides are deployedin sets of two situated to either side in the axial direction, and arejuxtaposed fluid-tightly against the movable member 122 in the axialdirection. As the slits 148 which have been formed in each of thesupporting plate springs 146 are situated at projected locations in theaxial direction, the slits 148 will overlap so as to communicate withone another.

A saucer shaped cover member 163 is attached to the opening section ofthe tubular portion 138 of the housing 136 so as to cover the openingsection of the tubular portion 138. The movable member 122 and the yokemember 124 situated inside the electromagnetic actuator 120 is therebyprotected from the outside by the tubular portion 138 and the covermember 163.

The lower end face of the outside peripheral section of the annularplate portion 140 of the housing 136 in the electromagnetic actuator 120is juxtaposed against the upper end face of the inside peripheralsection of the lower end plate fitting 84 b of the bracket member 80,and is bolted thereto. The electromagnetic actuator 120 is therebysecurely supported on the second mounting member 14 via the bracketmember 80.

As noted above, the end of the connector rod 112 on the opposite side ofthe rimming portion 118 thereof from the screw hole 114 is slipped intothe actuating rod 154, and the distal end section of the connector rod112 is then screwed into the fastening nut 160 so that the connector rod112 and the actuating rod 154 are connected to one another approximatelyalong the center axis of the mount 10.

Furthermore, the upper end face of the connector rod 112 is juxtaposedagainst the lower end face of the center section of the oscillatingplate 92, and a fastening bolt 162 is passed through the insertion hole96 from above the boss shaped projection 94 of the oscillating plate 92and screwed into the screw hole 114 of the connector rod 112. Themovable member 122 of the electromagnetic actuator 120 is therebyfastened to the oscillating plate 92 via the connector rod 112. From theabove description it will be appreciated that the electromagneticactuator 120 is situated to the opposite side of the oscillating plate92 from the pressure-receiving chamber 86.

The boss shaped projection 94 which projects from the upper end sectionof the oscillating plate 92 is linked to the partition member 32 via aplate spring 164. As depicted in FIG. 9, this plate spring 164 has athin annular disk shape made of spring steel or the like, with a centerhole 165 of circular shape formed in the center section. The insidediameter dimension of the plate spring 164 is smaller than the outsidediameter dimension of the boss shaped projection 94 of the oscillatingplate 92, while the outside diameter dimension of the plate spring 164is slightly smaller in comparison with the outside diameter dimension ofthe step portion 44 of the center hole 42 of the partition member 32. Aslightening sections, a plurality of slits 166 are formed in thediametrically medial section of the plate spring 164 and penetratethrough the plate in its thickness direction; and a plurality of boltinsertion holes 168 are formed at locations corresponding to the screwholes 50 which have been formed in the step portion 44 of the centerhole 42 of the partition member 32 in the outside peripheral section. Inthis embodiment, three slits 166 and three bolt insertion holes 168 areformed at equidistant intervals in the circumferential direction.

The center hole 165 of the plate spring 164 and the insertion hole 96 ofthe oscillating plate 92 are superposed at mutually projected locationsin the axial direction, and the fastening bolt 162 is then passedthrough the center hole 165 and the insertion hole 96, and threadablyfastened with the inside peripheral section of the plate spring 164positioned clamped between the head of the fastening bolt 162 and theboss shaped projection 94. The outside peripheral section of the platespring 164 rests on the step portion 44 of the center hole 42, the boltinsertion holes 168 of the plate spring 164 are aligned with the screwholes 50 of the step portion 44, and the outside peripheral section ofthe plate spring 164 is then bolted to the partition member body 34.With this arrangement, the plate spring 164 is disposed so as to extendin the axis-perpendicular direction on the opposite side of theoscillating plate 92 from the electromagnetic actuator 120, and theoscillating plate 92 is elastically linked to and supported in the axialdirection by the partition member 32, by means of the plate spring 164.That is, in association with actuation of the movable member 122 in theaxial direction, the plate spring 164 will experience elasticdeformation in the axial direction as well, and by virtue of beingpositioned in the axis-perpendicular direction by the plate spring 164,the oscillating plate 92 is maintained in a state with the oscillatingplate 92 and the cylinder shaped hole 46 positioned concentrically. Inother words, the gap 100 is maintained all the way around thecircumference between the outside peripheral edge of the oscillatingplate 92 and the peripheral wall of the cylinder shaped hole 46.

In the same way as the zone between the plate spring 164 and the seconddividing wall plate 38, the zone between the plate spring 164 and theoscillating plate 92 is filled with fluid through the slits 166 of theplate spring 164, so that the zone constitutes part of the secondpressure-receiving chamber 104.

In the automotive engine mount 10 of the construction described above,through flow of electrical current to the coils 126, 127 in onedirection about the diametrical axis of the magnetic pole portion 130 inthe electromagnetic actuator 120, an N pole is produced to thediametrical inward side of the yoke member 124, while an S pole isproduced to the diametrical outward side. When the current flow to thecoils 126, 127 is reversed, the N poles and S poles of the plurality ofpermanent magnets 128 attached to the yoke member 124 will weaken andstrengthen in alternating fashion. As a result, force in one directionand force in the other direction will act in alternating fashion uponthe movable member 122, causing the movable member 122 to undergoreciprocating motion to either side in the axial direction from itsequilibrium position in the absence of current flow (the positiondepicted in FIG. 1). From the above description it will be appreciatedthat the design of the output member that is passed through thediaphragm 74 and linked to the oscillating plate 92 incorporates themovable member 122 and the connector rod 112.

Through feedback control, such as adaptive control using the engineignition signal of the power unit as a reference signal and thevibration sensor signal of a component to be damped (such as the vehiclebody) as an error signal for example, electrical current to the coils126, 127 are controlled thereby in order to actuate oscillation of themovable member 122 in the axial direction. As a result, at times ofinput of low-frequency vibration such as engine shake, or at times ofinput of medium-frequency vibration such as engine idling or low speedrumble for example it will be possible, through actuation control of theoscillating plate 92 so as to effectively give rise to pressurefluctuations between the pressure-receiving chamber 86 and theequilibrium chamber 88, to effectively achieve vibration damping actionbased on resonance action of fluid through the first orifice passage 90,or vibration damping action based on resonance action of fluid throughthe second orifice passage 106.

In this embodiment in particular, the head of the fastening bolt 162which has been fastened to the boss shaped projection 94 of theoscillating plate 92, and the guide shaft portions 110 of the movableplate 108 are positioned in opposition a prescribed distance apart inthe axial direction. It is accordingly possible, for example, to actuatethe oscillating plate 92 upward so that the guide shaft portions 110 arepushed by the fastening bolt 162, thereby holding the movable plate 108in a state of abutment against the first dividing wall plate 36. Thethrough-holes 58 of the first dividing wall plate 36 is covered by themovable plate 108 and displacement of the movable plate 108 isconstrained, thereby making it possible to substantially prevent flowaction of fluid from arising through the second orifice passage 106,that is, to block off the second orifice passage 106. For this reason,as long as the second orifice passage 106 is maintained in a blocked offstate at times of input of vibration lying in the tuning frequency rangeof the first orifice passage 90, pressure leakage from thepressure-receiving chamber 86 through the second orifice passage 106will be prevented with a higher level of reliability so that thevibration damping effect afforded by the first orifice passage 90 may bemore effectively achieved.

It is also possible, for example, to actuate downward displacement ofthe oscillating plate 92 so that the rim shaped projection 98 of theoscillating plate 92 is held in a state of abutment against the innerflanged portion 48 of the partition member 32, and thus to prevent flowaction of fluid from arising between the second pressure-receivingchamber 104 and the equilibrium chamber 88, through gap 100 between theoscillating plate 92 and the cylinder shaped hole 46, in a yet morehighly reliable manner. Thus, by maintaining the outside peripheralsection of the oscillating plate 92 (the rim shaped projection 98)against the inner flanged portion 48 at times of input of vibrationlying in the tuning frequency range of the second orifice passage 106,pressure leakage from the second pressure-receiving chamber 104 throughthe gap 100 will be prevented in a yet more highly reliable manner, andthe vibration damping effect afforded by the second orifice passage 106may be more effectively achieved.

In this embodiment, the face of the inner flanged portion 48 positionedfacing the oscillating plate 92 is sheathed by a rubber cushioning layer170 that extends with generally unchanging thickness dimension about theentire perimeter. Since the oscillating plate 92 will strike the innerflanged portion 48 via the intervening rubber cushioning layer 170, theproblem of noise associated with striking can be ameliorated through thecushioning action of the rubber cushioning layer 170.

Additionally, at times of input of medium- to high-speed rumble in afrequency range higher than the tuning frequency range of the firstorifice passage 90 and the second orifice passage 106, actuating forcecorresponding to the vibration in question is directed onto theoscillating plate 92. The internal pressure of the pressure-receivingchamber 86 which incorporates the first and second pressure-receivingchambers 102, 104 is thereby controlled on the basis of actuatedoscillation of the oscillating plate 92 to effectively provide positiveand active vibration damping action against the high frequencyvibration.

In this embodiment in particular, the resonance frequency of fluidflowing through the through-holes 58, 68 in the first and seconddividing wall plates 36, 38 and through the circular zone 72 is tuned toa high frequency range such as medium- to high-speed rumble in order toachieve active vibration damping action by the oscillating plate 92; andin combination therewith, pressure fluctuations arising in the firstpressure-receiving chamber 102 and the second pressure-receiving chamber104 on the basis of actuated oscillation of the oscillating plate 92 istransmitted efficiently utilizing the resonance action of the fluidcaused to flow through the through-holes 58, 68 and the circular zone72. The vibration transmission characteristics of the first mountingmember 12 and the second mounting member 14 linked by the main rubberelastic body 16 may then be adjusted through positive and active controlof the pressure fluctuations arising in the first pressure-receivingchamber 102 and the second pressure-receiving chamber 104, toadvantageously produce the desired vibration damping action.

The oscillating plate 92 is supported positioned in theaxis-perpendicular direction at one axial side thereof by the movablemember 122 of the electromagnetic actuator 120, and is supportedpositioned in the axis-perpendicular direction at the other axial sidethereof by the plate spring 164. The oscillating plate 92 is therebysupported positioned in the axis-perpendicular direction to either sidein the axial direction with respect to the partition member 32, therebyaffording excellent suppression of displacement of the oscillating plate92 in the axis-perpendicular direction, as well as of displacement in atwisting direction.

As a result, actuation efficiency of the oscillating plate 92 in theaxial direction is improved, and the desired vibration damping actionwill be effectively achieved. Additionally, the likelihood of theoscillating plate 92 contacting the peripheral wall of the cylindershaped hole 46 will be minimized, thereby avoiding the anxiety of damageetc. resulting from such contact.

Additionally, because the oscillating plate 92 is supported at eitherside of its center axis by the partition member 32, problems caused byinterference of the oscillating plate 92 with the cylinder shaped hole46 can be eliminated, while keeping the gap 100 between the outsideperipheral face of the oscillating plate 92 and the inside peripheralface of the cylinder shaped hole 46 sufficiently small and providing theopposed sections of the oscillating plate 92 and the cylinder shapedhole 46 in the axial direction with considerable length in the axialdirection. This has the effect of increasing the piston surface area ofthe opposed sections of the oscillating plate 92 and the cylinder shapedhole 46, while inhibiting pressure leakage from the pressure-receivingchamber 86 through the gap 100 so as to stabilize and enhance theefficiency of pressure control of the pressure-receiving chamber 86.

Furthermore, in the embodiment, employing the plate spring 164 affordsthe advantage of allowing sufficient displacement of the oscillatingplate 92 in the axial direction, while effectively positioning it in theaxis-perpendicular direction. Moreover, as the axial dimension of theplate spring 164 is typically small, problems in terms of ensuringadequate space or larger size in association with installation of theplate spring 164 in the mount 10 are eliminated.

While the present invention has been described in detail in itspresently preferred embodiment, it is to be understood that theinvention is by no means limited to the details of the illustratedembodiment and may be embodied with various changes, modifications andimprovements which may occur to those skilled in the art, withoutdeparting from the spirit and scope of the invention.

For example, the shape, size, construction, number, placement and otheraspects of the oscillating plate 92, the plate spring 164, the firstorifice passage 90, the second orifice passage 106, the filter orifice,the movable plate 108 etc. are not limited to those taught herein by wayof example. In particular, the second orifice passage 106, the filterorifice, the movable plate 108 may be provided on an as-needed basis andare not essential elements.

Also, whereas in the embodiment hereinabove the oscillating plate 92 isfurnished with a single plate spring 164 only, the plate spring 164could instead have a stacked construction in which a plurality of platesprings 164 are stacked in the actuation direction of the oscillatingplate 92 as depicted in FIG. 10, for example. In this case, theplurality of plate springs 164 may be juxtaposed in intimate contact, orjuxtaposed at projected locations while respectively spaced apart in theactuation direction of the oscillating plate 92. In the description withreference to FIG. 10 and other embodiments different from the embodimenthereinabove, elements substantially identical in construction to theembodiment above are designated by like reference numerals and are notdiscussed in detail.

Furthermore, where a plurality of plate springs 164 are juxtaposed asdepicted in FIG. 10, the slits 166 which have been formed as lighteningsections in the plate springs 164 may be juxtaposed so as to communicatewith one another.

Additionally, the electromagnetic actuator employed may be one with aconstruction in which, as shown by way of example herein, the permanentmagnets 128 are disposed on the slider side while the coils 126, 127 andthe yoke member 124 are disposed on the stator side so that the N polesand S poles on the slider side increase and decrease in alternatingfashion by means of the magnetic field created when current is passedthrough the coils 126, 127, causing the slider to undergo reciprocatingmotion; or an electromagnetic actuator of conventional construction suchas that disclosed in Japanese Unexamined Patent Publication No.2000-213586 or U.S. Pat. No. 6,422,546, in which, using a singlepermanent magnet, the slider is actuated to one side in the axialdirection through the action of a magnetic field created when current ispassed through a coil, while the slider is actuated to the other side inthe axial direction using the urging force of a coil spring or the like.

Moreover, the partition member body 34 need not be a single component asshown herein by way of example. Instead, several components may beassembled together, for example, which will have the effect of improvingfreedom in tuning of the shape, length, cross sectional area etc. of thefirst and second orifice passages.

Additionally, whereas in the embodiment hereinabove the secondpressure-receiving chamber 104 and the equilibrium chamber 88communicate with one another through the second orifice passage 106, itwould be possible for the first pressure-receiving chamber 102 and theequilibrium chamber 88 to communicate with one another, for example.

Also, while in the embodiment hereinabove the movable plate 108 isdisposed within the circular zone 72 that constitutes the filterorifice, the movable plate 108 could be disposed at a separate locationindependent from the filter orifice.

Additionally, while the embodiment herein describes the inventionreduced to practice in an automotive engine mount, the invention couldbe implemented analogously in a body mount or diff mount, or invibration damping devices for various non-automotive vibrating bodies aswell.

1. A fluid filled type vibration damping device comprising: a rubberelastic body elastically connecting a first mounting member and a secondmounting member; a partition member supported on the second mountingmember; a pressure-receiving chamber whose wall is partly defined by therubber elastic body; an equilibrium chamber whose wall is partly definedby a flexible film; the pressure-receiving chamber and the equilibriumchamber being formed to either side of the partition member and filledwith a non-compressible fluid; a first orifice passage connecting thepressure-receiving chamber and the equilibrium chamber; an oscillatingplate defining another part of the wall of the pressure-receivingchamber; and an electromagnetic actuator for actuating oscillation ofthe oscillating plate, wherein the oscillating plate is constituted byincluding a cylinder shaped hole having a round tubular insideperipheral face formed in the partition member, and a piston shapedplate accommodated within the cylinder shaped hole with a gap providedbetween an outside peripheral face of the piston shaped plate and theinside peripheral face of the cylinder shaped hole so that the pistonshaped plate is axially displaceable within the cylinder shaped hole, anoutput member of the electromagnetic actuator is passed through theflexible film and linked to the piston shaped plate, a plate springextending in an axis-perpendicular direction is disposed to an oppositeside from the electromagnetic actuator with the piston shaped platetherebetween, with the oscillating plate being elastically linked to andsupported in an axial direction with respect to the partition member bythe plate spring, and the oscillation plate is supported at both sidesof a center axis thereof such that the oscillating plate at a first sidethereof in an axial direction is positioned and supported in anaxis-perpendicular direction by an output member of the electromagneticactuator, and another side thereof in the axial direction is positionedand supported in the axis-perpendicular direction by the plate spring.2. The fluid filled type vibration damping device according to claim 1,wherein the electromagnetic actuator includes a design whereby theoutput member is elastically supported with respect to a housing of theelectromagnetic actuator by a supporting plate spring that extends inthe axis-perpendicular direction.
 3. The fluid filled type vibrationdamping device according to claim 1, wherein the pressure-receivingchamber is partitioned by a dividing wall member that is disposed in amedial section of the pressure-receiving chamber in order to form toeither side of the dividing wall member a first pressure-receivingchamber whose wall is partly defined by the rubber elastic body and asecond pressure-receiving chamber whose wall is partly defined by theoscillating plate, and a filter orifice is provided for connecting thefirst pressure-receiving chamber and the second pressure-receivingchamber.
 4. The fluid filled type vibration damping device according toclaim 3, wherein a second orifice passage is provided connecting thesecond pressure-receiving chamber and the equilibrium chamber, with thesecond orifice passage being tuned to a higher frequency range than thefirst orifice passage, the filter orifice is formed in the dividing wallmember, and a movable plate is displaceably disposed in the filterorifice such that pressure of the first pressure-receiving chamber isexerted on a first face of the movable plate while pressure of thesecond pressure-receiving chamber is exerted on another face of themovable plate.
 5. The fluid filled type vibration damping deviceaccording to claim 1, wherein the cylinder shaped hole is formed in acenter section of the partition member so as to extend in a direction ofopposition of the pressure-receiving chamber and the equilibriumchamber, with the wall of the equilibrium chamber being defined in partby an outside peripheral section of the partition member about thecylinder shaped hole, and an outside peripheral face of the partitionmember has a tapering contour decreasing in diameter from a first axialend of a pressure-receiving chamber side thereof towards another axialend on an equilibrium chamber side.
 6. The fluid filled type vibrationdamping device according to claim 1, wherein a plurality of platesprings are disposed in a stacked structure by being juxtaposed in adirection of actuation of the oscillating plate.
 7. The fluid filledtype vibration damping device according to claim 6, wherein a lighteningsection is formed in each plate spring, and the plurality of platesprings are juxtaposed with the lightening sections communicating withone another.
 8. The fluid filled type vibration damping device accordingto claim 4, wherein the oscillating plate is movable to push and holdthe movable plate in a state so that the second orifice passage isblocked off.
 9. The fluid filled type vibration damping device accordingto claim 4, wherein the oscillating plate is movable to be held in astate of abutment against the partition member so as to prevent flowaction of fluid from arising through the gap between the outsideperipheral face of the piston shaped plate and the inside peripheralface of the cylinder shaped hole.